Traditional Portland cement binders used in concrete form a calcium silicate hydrate (CSH) structure that begins to break down when exposed to high temperatures. Traditional concrete mixtures composed of aggregate, water, and Portland cement are typically limited to service temperatures of 100° C. or less. Higher temperatures result in desiccation of the cement binder structure, leading to reduced volume, internal stresses, strength loss, and related failures. For example, temperatures above 800° C. can produce strength losses of at least 75% in traditional concretes. In addition, subsequent cooling from these high temperatures results in large increases in shrinkage and integrity loss due to reduced volume of the cement binder.
For high temperature applications, various formulations utilizing refractory cements containing enhanced alumina contents and expansion-resistant aggregate fillers are used. Compared to Portland cement, refractory cement binders are substantially more expensive and are only used for special high temperature applications. However, Portland cement is unsuitable for high temperature applications because of degradation.
For example, Portland cement concrete is not typically used to manufacture decorative fire logs used in gas fireplaces. Instead, a ceramic material is typically used. In general, artificial fire logs are used in many gas or propane fireplaces as inserts designed to resemble real wooden logs. Artificial fire logs are typically formed from ceramic fiber materials.
Accordingly, there is an ongoing need for improved refractory materials and refractory material production processes, including concrete fire logs and processes for producing concrete fire logs.